Integrated circuit (IC) devices and other electronic components are normally tested to verify the electrical function of the device and certain devices require high temperature burn-in testing to accelerate early life failures of these devices. Wafer probing is typically done at temperatures ranging from 25 C.-125 C. while typical burn-in temperatures range from 80 C. to 140 C. Wafer probing and IC chip burn-in at elevated temperatures of up to 200 C. has several advantages and is becoming increasingly important in the semiconductor industry.
The various types of interconnection methods used to test these devices include permanent, semi-permanent, and temporary attachment techniques. The permanent and semi-permanent techniques that are typically used include soldering and wire bonding to provide a connection from the IC device to a substrate with fan out wiring or a metal lead frame package. The temporary attachment techniques include rigid and flexible probes that are used to connect the IC device to a substrate with fan out wiring or directly to the test equipment.
The permanent attachment techniques used for testing integrated circuit devices such as wire bonding to a leadframe of a plastic leaded chip carrier are typically used for devices that have low number of interconnections and the plastic leaded chip carrier package is relatively inexpensive. The device is tested through the wire bonds and leads of the plastic leaded chip carrier and plugged into a test socket. If the integrated circuit device is defective, the device and the plastic leaded chip carrier are discarded.
The semi-permanent attachment techniques used for testing integrated circuit devices such as solder ball attachment to a ceramic or plastic pin grid array package are typically used for devices that have high number of interconnections and the pin grid array package is relatively expensive. The device is tested through the solder balls and the internal fan out wiring and pins of the pin grid array package that is plugged into a test socket. If the integrated circuit device is defective, the device can be removed from the pin grid array package by heating the solder balls to their melting point. The processing cost of heating and removing the chip is offset by the cost saving of reusing the pin grid array package.
The most cost effective techniques for testing and burn-in of integrated circuit devices provide a direct interconnection between the pads on the device to a probe sockets that is hard wired to the test equipment. Contemporary probes for testing integrated circuits are expensive to fabricate and are easily damaged. The individual probes are typically attached to a ring shaped printed circuit board and support cantilevered metal wires extending towards the center of the opening in the circuit board. Each probe wire must be aligned to a contact location on the integrated circuit device to be tested. The probe wires are generally fragile and easily deformed or damaged. This type of probe fixture is typically used for testing integrated circuit devices that have contacts along the perimeter of the device. This type of probe cannot be used for testing integrated circuit devices that have high density area array contacts. Use of this type of probe for high temperature testing is limited by the probe structure and material set.
High temperature wafer probing and burn-in testing has a number of technical challenges. Gold plated contacts are commonly used for testing and burn-in of IC devices. At high temperatures, the gold plated probes will interact with the solder balls on the IC device to form an intermetallic layer that has high electrical resistance and brittle mechanical properties. The extent of the intermetallic formation is dependant on the temperature and duration of the contact between the gold plated probe and the solder balls on the IC device. The gold-tin intermetallic contamination of the solder balls has a further effect of reducing the reliability of the flip chip interconnection to the IC device. Another problem caused by the high temperature test environment is diffusion of the base metal of the probe into the gold plating on the surface. The diffusion process is accelerated at high temperatures and causes a high resistive oxide layer to form on the surface of the probe contact.